Lead-acid battery plates are conventionally made by making a battery grid from lead or a lead-based alloy by gravity casting or by expanding strip. A wet paste consisting usually of a mixture of lead and lead oxide is applied to the grid. The paste may also contain a number of additional agents such as, for example, expanders. The pasted plates are then cured and dried under carefully controlled conditions. This curing and drying step is a slow process that takes from 48 to 72 hours to complete. During the curing and drying, oxidation of metallic lead and formation of basic lead sulfate compounds from lead oxide take place, and the microstructure of the active material precursor changes to yield a mechanically strong plate. The cured plates are then assembled into a battery which is filled with electrolyte, and an electrical current is passed through the plates for the formation of charged plates. The charged battery contains a number of positive plates containing lead oxide as the active material and a number of negative plates containing metallic lead as the active material.
In this conventional manufacture of lead-acid batteries, the controlled curing and the formation of charged plates are time-consuming. The literature on lead-acid battery manufacture is full of attempts and schemes to speed up the manufacture.
Much effort has also been expended to ensure that the cured battery plates possess the required porosity. One such effort includes the incorporation of a salt in the active material which is subsequently leached from the plate leaving a porous layer of active material. According to U.S. Pat. No. 1 467 749, preformed storage battery plates are made by mixing alkali metal bisulfate and a non-conductive binding substance with lead peroxide and another lead compound, applying the mixture to a conductive support, and removing the soluble material from the pasted support. D.E. Hall (J. Electrochem. Soc. 136, 5, May 1989, p 1278-1282) teaches that porous lead plates are made by sintering lead powder mixed with sodium sulfate and leaching the sulfate with water from the sintered plates. The sintering is carried out at 320.degree. C. for about one hour in a reducing atmosphere. According to U.S. Pat. No. 3 663 297, a porous zinc electrode is made by cleaning zinc powder, mixing it with an inorganic water-soluble salt, packing the mixture around a metal screen, and heating and soaking the assembly to remove the salt. Similar-type processes for making a porous metal structure have been disclosed in U.S. Pat. Nos. 3 322 535 and 3 337 336. 3,337 336.